Short Communication
Osman Adiguzel
Abstract
Shape memory alloys take place in a class of smart materials by exhibiting a peculiar property called shape memory effect. This property is characterized by the recoverability of two certain shapes of material at different temperatures. These materials are often called smart materials due to the functionality and their capacity of responding to changes in the environment. Shape memory materials are used as shape memory devices in many interdisciplinary fields such as medicine, bioengineering, metallurgy, building industry and many engineering fields. Shape memory effect is performed thermally by heating and cooling after first cooling and stressing treatments, and this behaviour is called thermo elasticity. Shape memory effect is based on a solid state phase transition, martensitic transformation, and this transformation is characterized by changes in the crystal structure of the material. Shape memory effect is result of successive thermally and stress induced martensitic transformations. Shape memory alloys exhibit thermo elasticity and super elasticity by means of deformation in low temperature product phase and high temperature parent phase region, respectively. Super elasticity is another characteristic of shape memory alloys and performed by stressing and releasing the material in parent phase region. Loading and unloading paths are different in stress strain diagram and cycling loop reveals energy dissipation. The strain energy is stored after releasing and these alloys are mainly used as deformation absorbent materials in control of civil structures subjected to seismic events, due to the absorbance of strain energy during any disaster or earthquake.